1. Field of the Invention
This invention relates to a color-correcting filter glass which selectively absorbs light of wavelengths in the range of about 400 about 500 m.mu. and light of wavelengths both in the range of about 400 to about 500 m.mu. and in the range of about 600 to about 700 m.mu..
2. Description of the Prior Art
In color printing, gelatin films which selectively absorb the wavelength of blue, red, green and yellow light, etc. have been used heretofore as color-correcting filters. Gelatin films have the advantage that they are inexpensive, and can be relatively easily dyed to produce filters of various colors.
But since they are susceptible to degeneration or discoloration during use, they must be exchanged within relatively short peiods of time in order to always obtain prints in a stable manner. Hence, gelatin filters are not suitable for incorporation in devices with complicated mechanisms in which exchange is difficult.
On the other hand, conventional colored glasses are unsuitable for color correction because they have inferior light absorption characteristics to gelatin filters despite their color tones being similar to those of gelatin filters. An example of such colored glasses is a yellow glass based on a Ag colloid. Since this yellow glass must be melted under reducing conditions, it is difficult to obtain a glass which is free from bubbles and striae and which has a uniform color, and also adverse effects occur with such a glass due to scattering of light. It is known that a metaphosphate glass containing nickel has a yellow color. However, a metaphosphate glass is not practical because of its extremely poor chemical resistance.